Final answer:
Rachel Carson's 'Silent Spring' is focused on pesticide toxicity, especially the negative effects of DDT on the environment and wildlife, contributing to important environmental reforms. Therefore, the most appropriate correct option is A.
Step-by-step explanation:
Rachel Carson's landmark book Silent Spring primarily focuses on the environmental problems associated with pesticide toxicity, particularly highlighting the impact of DDT. The book provides a detailed examination of the ecological dangers posed by the overuse of chemical pesticides, including bioaccumulation and its effects on wildlife such as birds and fish. Carson's influential work sparked a significant change in environmental policy and led to increased awareness and legislative action against the unregulated use of pesticides.